The -900 made its maiden flight on 19 October 2017 and received its EASA type certificate on 26 September 2018; it was first delivered to TAP Air Portugal on 26 November 2018 and entered service on 15 December.

After the A320neo launch in December 2010 and its commercial success, the largest airline of Malaysia – an all-Airbus operator – AirAsia asked Airbus to re-engine the A330.

[6] Airbus sales chief John Leahy's argument was that the lower purchase price of an A330 even without new engines make the economics of buying an A330 competitive at midrange routes with that of the Boeing 787.

[10] In the 250-300-seat market, CIT Group believed an A330neo enables profitability on shorter ranges where the longer-range A350 and Boeing 787 are not optimised.

CIT said that the A350-800 was not as efficient as it would like, and Air Lease Corp. added that the company did not consider it reasonable to take the A350-800 and A330neo as they saw no sustainable coexistence of the two aircraft.

Its range would increase by 400 nautical miles (740 km; 460 mi) and although 95% of the parts would be common with the A330ceo, maintenance costs would be lower.

New winglets, 3.7 metres wider and similar to those of the A350 XWB, still within ICAO category E airport requirements, along with new engine pylons, would improve aerodynamics by 4%.

[21] Boeing Vice Chairman and Commercial Airplanes CEO Ray Conner dismissed the A330neo as 2004 revamp which cannot match the 787's direct operating costs, being 20,000 lb (9.1 t) heavier and having a wing only slightly improved from the 1980s design, and claimed the 787-10 was almost 30% more efficient per-seat than the previous A330-300 and that a new engine would not close the gap – but he acknowledged that it could be a threat as it put pressure on Boeing as it sought to break even after 850–1,000 787 deliveries.

[23] Final assembly of the first aircraft, an A330-900, started in September 2016 at the Airbus Toulouse site with the joining of the wings to the centre fuselage at the station 40.

[24] In December 2016, the programme schedule slipped by six weeks due to marginal engine development at Rolls-Royce, and launch customer TAP Air Portugal projected its first A330neo would be delivered in March 2018.

[30] Major structures of the first A330-800 were entering production in October 2017: high-lift devices are installed on the wing in Bremen, fuselage sections are built in Hamburg, the centre wing-box in Nantes, titanium engine pylons in Toulouse and sharklet wingtips in Korea.

[34] In April 2020, the production rate decreased from 3.5 to 2 per month due to the impact of the COVID-19 pandemic on aviation, and finished planes were stored while waiting for deferred deliveries.

[37] It should establish certain maximum operating points and achieve an initial handling qualities assessment including at high angle of attack.

[39] The second test aircraft made its maiden flight on 4 December, to be used to validate aerodynamic & engine performance and airline operations.

Its flight envelope was fully opened including flutter and stall tests to complete powerplant calibration and strake configuration has been frozen.

[2] The airline should receive 15 more A330neos in 2019 and fly the A330-900 from Lisbon to Chicago O'Hare and Washington Dulles from June 2019, both five times a week.

The heavier structure allows a transpacific range and is balanced by a weight-reduction effort, keeping the same empty weight and payload.

Retaining 99% spares commonality, it offers 6 t (13,000 lb) more payload while strengthening the landing-gear and extending the time before overhaul interval from 10 to 12 years.

However, this gain is negated by 3%–2% by additional weight, and 1% due to engine drag, but the sharklets and aero optimization regain 4%, restoring the advantage to 12%.

[7] Since the fan is enlarged from 97 to 112 in (250 to 280 cm), the nacelles are mounted higher, necessitating extensive CFD analysis to avoid supersonic shock wave interference drag, as is the first slat's dog-tooth.

[70] Airbus unveiled a distinctive cockpit windscreen to be featured on the A330neo, similar to that on the A350,[71] and promised a new interior concept offering a better passenger experience on the A330neo.

The Trent 1000 TEN (Thrust, Efficiency, New Technology) engine was under development for the 787-10, but Rolls-Royce intended to offer a broad power range.

[77] After the first flight of the -900 on 19 October 2017, Hawaiian Airlines (then the only customer for the -800) considered changing its order to six -800s, seeking best to fit its current network to Asia and North America whilst allowing for future growth, possibly to Europe.

At this time, Boeing intends to launch its New Midsize Airplane no earlier than 2027, affording Airbus opportunities with the 95 operators of the A330ceo.

[89] Airbus could limit its MTOW to 200 t (440,000 lb) and derate its engines to 68,000 lbf (300,000 N) to optimise for the shorter routes to be targeted by the Boeing NMA, with the A321XLR tackling the lower end of the same niche.

[52] The first aircraft, configured with 226 seats including 23 in business class, was to be delivered to Kuwait Airways in March, but the airline postponed delivery until the third quarter of 2020 amid the COVID-19 pandemic.

[99] Amazon Air and UPS Airlines pushed for a freighter version, stretching the A330-900 to carry more cargo over a shorter range, but retired passenger 767 and A330 aircraft provide a lot of conversion potential.

[1] On 11 April 2023, Airbus delivered the 100th A330neo, an A330-900, to German charter airline Condor Flugdienst GmbH, which would lease it from AerCap.

[155] At entry into service in 2018, sales were disappointing and A330 production was to be cut to 50 in 2019 down from 67 in 2017: while it was the widebody with the largest operator base with 1,390 deliveries since 1993, the fleet was still very young with only 46 aircraft retired.

[158] In May 2019, Airbus's chief commercial officer made clear the company has a “rock”, the A321neo, and a “hard place”, the A330-800, for any airframer intending to bring a new airplane into the middle of the market at a time when Boeing was mired in the 737 MAX crisis.